The impact of the life sciences on psychology
Scientific psychology as we know it today is the offspring of the marriage of philosophy and the life sciences. All psychology prior to the nineteenth century lacked a foundation of sound biological knowledge. That does not mean to say that it was all entirely worthless, but it does mean that psychological speculation lacked a very important constraint. Many psychologists from Aristotle onwards had grasped the fact that psychology had roots in biology. Indeed Brett has expressed the view that more than a century before Aristotle ‘Alcmaeon of Croton began the long history of the influence that a study of the human organism has had on theories of the soul.’ 1 These studies, however, were handicapped by inadequate techniques for investigating organisms, and a lack of reliable knowledge. Even as late as the middle of the eighteenth century when Hartley attempted to propound a physiological psychology, the physiological basis of his observations was largely speculative. 2 Though the life sciences began to develop experimentally in the seventeenth century, it was not until the early nineteenth that they were sufficiently advanced to make much of an impact on psychology. Their development over the last two hundred years has been spectacular; indeed, it has been one of the greatest achievements in the whole history of human thought. The influence of this progress on psychology has steadily increased from the beginning of the nineteenth century up to the present day, and it will no doubt continue to be an important, though not an exclusive, influence in the future. We must briefly examine, therefore, some of the major developments in the life sciences of particular concern to psychology.